Even Li Chunfeng, who smiled in the past, still had a trace of unruly smile on the corner of his mouth, today's incident in Huancai Pavilion is afraid that it will become a good story in Chang'an City for a while.

As our protagonist, Li Chunfeng is still immersed in the black and sweet country at the moment......

"Li Lang, wake up, wake up."

"Sun Weng, Chunfeng is really okay, right?"

"Don't worry, Daoist Yuan, Li Lang is fine."

Li Chunfeng felt that someone was patting his cheek, and at the same time, a call came from his ears.

"Li Lang, wake up, wake up ......"

Consciousness gradually recovered, and Li Chunfeng slowly opened his eyes: "Master? Sun Daochang? ”

Slowly sitting up from the bed, Li Chunfeng touched his head, looked around, and said, "Where is this?" ”

"We're home." Yuan Tiangang said, "Chunfeng, how do you feel now?" ”

Li Chunfeng nodded and said, "It's okay, it's just that my head is a little heavy." ”

Look at the sky outside, but at four or five o'clock in the afternoon, the sun is setting in the west, and the sun shines on the ground through the window, which makes this empty room a little more lively.

"By the way, what's wrong with that Huo Xiaoyu?"

Yuan Tiangang said: "The contract has been returned to Yu Niang, and she can be regarded as regaining her free body." ”

"That's good."

After a short silence, Sun Simiao on the side said: "When you were in the Huancai Pavilion, Li Lang, you can calculate such a huge number, I don't know how to calculate it?" And what does that time and what does it mean? ”

At this moment, Sun Simiao's expression was serious like a student, and Li Chunfeng scratched his head: "Well, this is a special calculation method." ”

Speaking of this, Li Chunfeng got up from the bed, then pushed open the door and walked out of the room.

"I want to hear about it." Yuan Tiangang and Sun Simiao also followed.

The autumn afternoon sun illuminated the entire courtyard, and I saw Li Chunfeng take a wooden stick from the side and write and draw on the ground.

"On the chessboard, the first grid is 1 penny, and the back grid has twice the number in front of it." Speaking of which, Li Chunfeng wrote "1X2" on the ground.

"The third cell is twice as large as the second one, which is 1X2X2."

"THE FOURTH CELL IS TWICE AS LARGE AS THE THIRD, WHICH IS 1X2X2X2X2."

Writing this, Yuan Tiangang opened his mouth and said: "Chunfeng, is it possible that the symbol you have here represents the number?" ”

Li Chunfeng was stunned for a moment, and then began to realize that there were no Arabic numerals in Datang, and nodded: "Yes, this represents one, this represents two, and the x in the middle represents the meaning of doubling the front." ”

"It's wonderful, using symbols instead of words, but it looks a lot more concise." Sun Simiao drew inferences, "If x represents double, wouldn't it be a truth to rotate it into + to represent plus?" As he spoke, Sun Simiao drew a "+" sign on the ground.

"Uh...... That's right. ”

"If you take the + away and turn it into — doesn't that mean a decrease?" Yuan Tiangang also made a stroke on the ground with a wooden stick.

Li Chunfeng looked at the two in surprise: "Genius, both of them are really geniuses." ”

Sun Simiao stroked his beard and said, "Hahaha, Li Lang has won the award, we are just drawing inferences." ”

"If you take out 1 alone, the rest of the single looks at it, it is 2 doubled again and again, could it be how many powers of 2 Li Lang said?"

"That's right." The more Sun Simiao analyzed, the more surprised Li Chunfeng became, and he couldn't imagine that the IQ of the ancients was so high.

Yuan Tiangang said: "However, even if there are these symbols instead, I still don't know the real result?" ”

"Yes, what's the use of such symbols?" Sun Simiao was also puzzled.

Li Chunfeng was also helpless in his heart, how should he explain it to these two people?

At this moment, Yuan Tiangang, who was thinking alone, seemed to remember something: "Oh, I remember, there seems to be a solution in "Nine Chapters of Arithmetic". ”

"Nine Chapters of Arithmetic?" Li Chunfeng was stunned, he heard this thing for the first time.

"Chunfeng, you wait for me."

After that, Yuan Tiangang hurriedly ran into the room, and after rummaging through the cabinets for a while, he walked out with a very broken ancient book.

"Chunfeng, come and see here."

Under Yuan Tiangang's rummaging, I saw a page of small characters and a few pictures appear in front of Li Chunfeng.

"Look here, the book says, today there are fifteen steps wide, from sixteen steps. Asked for the geometric answer of the field: one acre. Following the direction of Yuan Tiangang's finger, I saw that after these lines, there was a picture with a rectangle drawn on it, and the annotation "Fifteen steps x sixteen steps to get two hundred and forty, one mu" was written on the side.

"It turns out that the symbol 'x' has been mentioned in "Nine Chapters of Arithmetic", wonderful, wonderful." Sun Simiao stroked his beard, "Li Lang, I didn't expect you to study this book like this. ”

"Shame shame!" Li Chunfeng could only smile back with an embarrassed smile, since there is a record in the book, there is no need for Li Chunfeng to explain.

Yuan Tiangang said: "However, how did you get two hundred and forty in these fifteen steps x sixteen steps?" Chunfeng, do you have any insights? ”

"Huh? Oh, I guess, it should be. ”

So, Li Chunfeng picked up the wooden stick, and scribbled on the ground again, muttering: "Five times six gets thirty, carry three to get zero, one times one gets one, one times six gets six, one times five gets five, and finally add up ......"

When Li Chunfeng used the method of modern primary school students to calculate the result of 15x16, Yuan Tiangang and Sun Simiao were stunned.

"I, Yuan Tiangang, am so old, I can't imagine that I can still see such a calculation technique, amazing, amazing."

"Old decay is also an eye-opener."

Yuan Tiangang praised: "Such a calculation method should be recorded and left for future generations." ”

"Not bad, not bad." Sun Simiao also agreed.

I saw Yuan Tiangang return to the house, brought a pen and paper, and wrote according to the method that Li Chunfeng had just calculated on the ground: "Chunfeng and so on: through Yun Guangcong, multiply each other to get a step...... Before this note, the cloud accumulation is Tian Mi, which makes sense. Fuyun is called a power, complicated and inappropriate. Today's annotation, save the good and remove the wrong, slightly simplify, and leave it for future learning. ”

Yuan Tiangang wrote a lot of annotations, both power and accumulation, and Li Chunfeng didn't know what he was writing.

However, Li Chunfeng didn't know that he accidentally became the most authoritative commentator on "Nine Chapters of Counting" in history.

After writing this, Yuan Tiangang wanted to ask again: "Chunfeng, how about you tell me about this book of "Nine Chapters of Counting"?" ”

"Huh? This ...... "Like this ancient book, where can Li Chunfeng understand it?" For a moment, he was in trouble.

At this moment, there was a sudden sound of footsteps at the door, and then a voice came: "King Qin's special reward, where is Li Chunfeng?" ”

"Master, King Qin has sent someone." After saying this, Li Chunfeng walked quickly towards the gate.